The present invention relates to a method for making cards according to the precharacterizing clause of claim 1 and to a card made by this method. The present invention relates more specifically to a method for making cards, in particular smart cards or bank cards, laminated by cold pressing.
Although the description describes, above all, the particular case of the manufacture of smart cards, the invention may also apply to the manufacture of any other type of laminated cards, for example plasticized bank cards, telephone cards or visiting cards. However, the invention proves more particularly advantageous for making cards intended to be used in a reader or automatic machine, especially for cards comprising an optical, magnetic or electronic storage portion.
Most known smart cards are made by laminating layers of various materials, such as polyvinyl chloride (PVC), polycarbonate (PC) or ABS, at least one of the layers accommodating an integrated circuit. Of the known manufacturing methods, hot-laminating methods and cold-pressing laminating methods are particularly important.
According to hot-laminating methods, the multiple layers forming a card are pressed between two plates and simultaneously heated to a temperature usually close to 160xc2x0, making it possible to fuse the layers together. A second cold press is sometimes used after the first, in order to cool the layers as a whole. Such methods are mentioned, in particular, in the patent documents WO 94/22111, DE 4444788, EP0163534 and EP0488754.
These methods are difficult to use in order to make smart cards comprising fragile electronic components which risk being destroyed by the intense heat and high pressure which are necessary. In particular, these methods are unsuitable for making cards comprising an accumulator or battery which does not withstand the intense heat released.
For this reason, cold-pressing laminating methods are sometimes preferred. According to these methods, the various layers forming the cards are assembled together by means of a binder or an adhesive which cures at a temperature below the melting point of the layers forming the card. WO 94/22110 describes an example of a method of this type. The various layers and the circuit are compressed in a press, the thickness and distribution of the binder being accurately controlled.
The outer faces of the card must be perfectly plane. This is particularly the case if the card is to be used in an automatic machine. For this purpose, the card manufacturers employ, for the outer faces, synthetic sheets which have undergone prior surface treatment. This may involve, for example, hot pressing of the synthetic sheets against a smoothing plate, for example against a polished smoothing plate which makes it possible to eliminate surface irregularities. After smoothing, the synthetic sheets are cooled, detached from the polished metal surface and stacked, or sometimes wound on themselves, for the purpose of selling them and transporting them to the card manufacturer. The synthetic sheets obtained must be sufficiently smooth to be used as outer layers of the laminate.
The present invention relates to an improvement to the methods for making cards. In particular, the invention relates to an improvement to these methods which is particularly advantageous when it is applied to making cards intended to be used in automatic machines.
According to the invention, this improvement is afforded by means of the elements of the characterizing clause of claim 1.
More specifically, this improvement is afforded by carrying out the laminating operation by the cold pressing of the various layers and elements forming the laminated card between the smoothing plate, used during the previous hot-pressing smoothing operation, and at least one other plate. In this way, the synthetic sheets forming the outer layers of the laminated card are protected by the smoothing plates during transport and cold pressing. It is thus impossible for the outer surfaces of these sheets to be scratched or be covered with dust before or during the cold-pressing laminating operation.
By cold pressing is meant pressing without the addition of heat or, at least, pressing carried out at a temperature below the melting point of the outer layers of the laminate. If the outer layers are made of PVC, laminating is therefore carried out at a temperature below 140xc2x0 or, preferably, below 120xc2x0.